As the physical dimensions of very large scale integrated circuits (VLSI) continue to shrink, it has become increasingly difficult to manufacture such integrated circuits in a reliable fashion. The sensitivity of a VLSI design to random defects increases as feature widths and spacing between features grow smaller. In addition, the presence of single vias (i.e., inter-layer connectors through a single via) is particularly undesirable. From the perspective of random-defect yield, a single via is especially likely to cause a chip failure because a spot-defect landing on a single via will create an open circuit. From the perspective of systematic yield, if vias are difficult to manufacture in a given process, a poorly created single via can cause a circuit open or a highly resistive connection, which can cause a circuit to fail. New manufacturing processes are particularly sensitive to yield problems that are related to the formation of vias. An example of a single via structure is shown with reference to FIGS. 1A and 1B.
For these reasons, a need exists for improved structures for implementing redundant vias in an integrated circuit physical design process, in order to reduce the complexity of the manufacturing process, maintain high wiring density, and maximize manufacturing yield.